Solar power output up 10 percent in new panels, CWRU awarded federal grant to test durability (The Plain Dealer)

Case Western Reserve University has been awarded a $1.47 million federal grant to determine the durability of a new, more powerful solar panel design already commercially available.

The hot new design -- known in the industry as "Passivated Emitter Rear Cell," or PERC -- typically boosts the output of an off-the-shelf solar panel by 10 percent. And manufacturers can make the design changes without major re-tooling of production lines.

What this means for customers is that installers can use fewer solar panels to get the same level of power, lowering the overall cost of a project. Or, if space is not an issue and the budget not as critical, installers can boost the total output of a solar array.

"Many of our module suppliers are switching over to PERC cells in their manufacturing lines because of the improved efficiencies," said Alan Frasz, president of Cleveland-based Dovetail Solar and Wind. "Our customers are not asking for PERC cells. They simply ask about overall efficiency."

The major challenge now facing the industry is demonstrating the long-term reliability of PERC modules compared to traditional crystalline silicon modules, said Roger French, CWRU's Kyocera Professor of Materials Science and director of the school's Solar Durability and Lifetime Extension (SDLE) Research Center.

Since opening in 2012, the SDLE research center has been busy trying to degrade or wear out dozens of solar panels from major manufacturers. In addition to an outdoor solar field, the center's labs are packed with equipment to accelerate the normal wear that solar panels sustain from weather extremes and air pollution, subjecting them to extreme temperatures and lighting conditions, while carefully measuring power output.

The center works directly with manufacturers and with a network of other academic solar research labs.

French said a PERC solar panel is manufactured with a couple of simple changes to the interior architecture of the standard solar cell, including the addition of a reflective sheet at the bottom of the cell.

In a conventional solar panel, some of the light that passes through the solar cell creates a flow of electrons. The light is then absorbed at the bottom of the solar panel.

In a PERC solar panel, the light that makes it to the bottom of the solar panel is concentrated and reflected back up, giving the solar cells a second shot at generating a flow of electrons.

A standard silicon solar cell uses a portion of the light passing through it to create electrons. It can and achieve an efficiency of up to 18 percent. A change in the architecture and the addition of a reflective material at the bottom of the newly available PERC solar cell bounces the light back up through the silicon cell for a second pass and increases the efficiency to 20 percent without a significant increase in cost. A solar array built with PERC solar cells requires fewer solar panels to generate the same output of arrays using old-design panels. The PERC solar cells also generate power at lower light levels. (DuPont Co. )

"You get two chances to convert the light into an electron," said French. "This is a rather simple change to a cell.

"A PERC cell is very much like cells that manufacturers were making last year. But you get 10 percent more electricity. That is a gigantic difference. And the [manufacturing] cost of doing this is very small."

So what could go wrong?

The concern is that the jump in power production might somehow make PERC solar cells degrade faster than conventional cells. Or that the new reflective material at the bottom of the solar panel might be more sensitive "to the generally hostile conditions of being outside and exposed to the weather for 25 years."

The change in the interior architecture of a PERC cell also means that the electrical current is flowing through a smaller area of a cell, and the question is whether that might cause faster degradation.

The bottom line for the lab: "Our project is to demonstrate and validate the reliability and durability of these and make sure there are no hidden affects that need to be figured out and compensated for," said French.

The $1.47 million three-year grant includes regular progress milestones, meaning CWRU has not and will not receive one check for the entire amount.

The grant is part of $46.2 million in solar research funds awarded to 48 projects across the country by the U.S. Department of Energy's "SunShot" R&D program.

(U.S Department of Energy)

SunShot works with industry and university laboratories, national laboratories and state and local governments to drive down the cost of solar and accelerate its deployment.

The goal is to reduce the cost of solar power so that by 2030 its cost is equal to or less than the cost of power generated by conventional power plants.